Tuning mechanism for dictating machine



INVENTOR.

R. E TROST 3,039,777

2 Sheets-Sheet 1 TUNING MECHANISM FOR DICTATING MACHINE June 19, 1962Filed Nov. 19, 1956 m E i United States Patent 3,039,777 TUNINGMECHANISM FOR DICTATING MACHINE Richard E. Trost, Dundee, 11].,assignor, by mesne assignments, to Victor Comptometer Corporation,Chicago,

111., a corporation of Illinois Filed Nov. 19, 1956, Ser. No. 623,017 9Ciaizns. (Cl. 27417) This invention relates in general to dictatingmachines and has more particular reference to tuning mechanism for suchmachines.

During a transducing operation of such a machine, one or both of thetransducer and record medium are so driven while they are in transducingrelationship that the transducer traces or retraces on the record mediuma path, the characteristic shape of which is determined by the relativemovement between the transducer and the record medium. Thus in atransducing operation of such a machine, it is possible to record andreproduce signals along such a path.

The term, tuning, as used herein, means initially establishing and, whenand where desired, re-establishing such relative positions of thetransducer and record medium as to provide the optimum transducingrelationship therebetween at the beginning of and throughout the tracingor re-tracing of such a path, whereby to promote fidelity in thetranslation of signal volume during a transducing operation.

Tuning usually involves the adjustment of the transducer transversely ofthe path being traced for bringing the tracer member of the transducerinto registration or alignment with that path. In the manufacture andassembly of such a machine with the usual tuning mechanism, the relativepositions of the record-medium support, hence the record medium, and thetransducer involves a strict adherence to close tolerances to ensure anacceptable transducing relationship between the transducer and recordmedium at the beginning of a transducing operation and to promote thedesired cooperation between the transducer and record medium during suchan operation. If such adherence to permissible tolerances isdisregarded, tuning by the usual adjustment of the tracer membertransversely of the path is diflicult of achievement at the beginning ofand throughout a transducing operation.

An object of the invention is the provision in a dictating machine ofnovel and improved tuning means for obviating strict adherence to closetolerances in the manufacture and assembly of the transducer and recordmedium supporting means in order to insure a proper transducingrelationship between the transducer and record medium.

Another object of the invention is the provision in such a machine oftuning mechanism which is itself adjustable for varying the limits andrange of the tuning adjustment.

A further object of the invention is the provision in such a machine ofnovel and improved tuning means for adjusting one of the transducer orrecord medium relative to the other of them not only transversely of thepath traceable on the record medium but also in a direction transverselyof that along which the transducer moves during a transducing operation,whereby to insure proper cooperation between the transducer and supportfor the record medium during a transducing operation.

Another object of the invention is the provision of novel and improvedtuning means or mechanism which is adapted for embodiment in a magneticbelt type dictating machine.

Other objects of the invention will become apparent 'ice from thefollowing description and the accompanying drawing which, by way ofexample, disclose a presently preferred embodiment of the invention.

In the accompanying drawing:

FIGURE 1 is a front elevational view of a machine embodying the featuresof the invention;

FIG. 2 is an end view from the right of FIG. 1;

FIG. 3 is a fragmentary View oriented according to FIG. 2, with some ofthe casing of the machine removed to reveal certain interior elements;

FIG. 4 is a partial sectional view, taken substantially along the lines4-4 of FIG. 1, and drawn on a larger scale and omitting certain portionsof the machine not essential to the present invention;

I FIG. 5 is a fragmentary horizontal sectional view taken approximatelyon lines 5--5 of FIG. 1 and drawn on a larger scale;

FiG. 6 is a rear view of certain of the elements of the interior of themachine and is taken approximately 011 lines 6-6 of FIG. 3 at adiiferent scale;

FIG. 7 is a detail view taken approximately on lines 7-7 of FIG. 4 andshown on a larger scale;

FIG. 8 is an exploded view of the tuning cam assembly; and

FIG. 9 is a large scale View of the tuning cam assembly and feed screw,taken approximately on lines 99 of FIG. 3.

While for convenience the present invention is shown as being embodiedin the magnetic type of dictating machine disclosed in the co-pendingUnited States Letters Patent application of Alfred E. Lorenz, Serial No.408,907, filed February 8, 1954, it will be understood by those skilledin the art that the invention is not limited to such a machine but maybe embodied to advantage in various types of dictating machines.

The illustrated type of machine, generally described, usually comprises,as shown in FIGS. 1, 4, and 6, a transducer head A, a rod or othersuitable support B therefor, a drivable carrier C for removably carryingand driving a record medium D, and a head-traversing drive connection Eincluding a rotatable threaded shaft or feed screw F In such a dictatingmachine, the head A is pivotally and slidably mounted on the support Bfor cooperation with the record medium D on the carrier C. The

transducer head is thus swingable in a direction substantially normal tothe record medium between a transducing position and a non-transducingposition with respect to the record medium on the carrier C. When thehead A is in its transducing position, it is movable by thehead-traversing drive connection E along the support B to traverse therecord medium D for recording or reproducing signals thereon. When thehead is in its nontransducing position, it is manually reciprocablealong the support B to position the head for a subsequent traversing ofall or a portion of the record medium.

As is well-known in the art and disclosed in the abovementionedapplication, the illustrated dictating machine comprises suitablesupporting, driving, control, amplifier, and casing means none of whichper se constitutes any part of the present invention and none of whichis therefore described in detail herein. It may be well, however, topoint out briefly that in the illustrated machine the transducer head Ais of the magnetic type; the carrier C comprises rotatable drive andtension rolls; the record medium D is an endless belt adapted to havemagnetic signals recorded thereon and to have such signals reproduced bythe transducer head A; the rotatable drive roll of the carrier C, therod B, and the rotatable feed screw F are mounted parallel to oneanother with the rod above and slightly forwardly of the feed screw andwith the drive roll forwardly of and slightly below the rod; and thedriving means is adapted to rotate the carrier C and the feed screw F intimed relationship, whereby during a transducing operation thetransducer head traces a helical path on the record medium with theconvolutions of the path spaced transversely of the record medium. 7 Asalready mentioned, the carrier C includes drive and tension rolls, nowdesignated by the reference numerals 14 and 15, respectively. The driveroll 14 is provided with a plurality of teeth or projections 16extending radially outwardly from its peripheral surface near an end ofthe roll for drivinglyengaging in spaced perforations 17 in the beltalong one of its margins. The tension roll 15 is mounted on a pivotallymounted arm 18 and is thus adapted to swing between an upper positionshown in broken lines in FIG. 2 and a lower or belt tightening ortensioning position shown in full lines in FIGS. 1 and 2. It also isreleasably positionable in an intermediate, belt receiving and removingposition, by means not shown herein but shown in the Lorenz applicationreferred to above.

The transducer head A and carriage therefor are preferably like thosedisclosed in the co-pending United States Letters Patent application ofAlfred E. Lorenz, Serial No. 489,20l,filed February 18,1955. i Such atransducer head comprises a suitable casing 19 and a transducer thereinhaving a tracer member 21 depending therefrom outside of the casing andbeing relatively thin in a direction transversely of the belt on thecarrier C. The transducer head A is adapted to be mounted on a carriage22 in such a manner that the tracer member 21, when the head A is in itstransducing position, is closely adjacent the drive roll 14 for lightlyengaging the record medium thereon. In the illustrated dictatingmachine, the engagement between the tracer member' and record medium foroptimum transducing relationship 'therebetween occurs in the verticalplane including the axis of the drive roll 14.

In the illustrated embodiment of the invention the carriage 22 includesa main body portion 23 (FIG. 4) mounted for m ovement in the mannerdescribed below and serving as the means directly to which the head A issecured. The head A has a rearwardly extending arm 24 shownforconvenience as being U-shaped in cross section (FTG. 6), and'fittedto the upper flat surface 25 of the body portion 23 and secured theretoby means such as screws 26 extending through slots 27 in the arm andthreaded into tapped holes in the body portion 23. The slots 27 arelongitudinally aligned and longitudinally elongated relative to. the arm24 for enabling substantial horizontal adjustment of the transducer headA in a direction transver'sely'of the axis of the drive roll 14.

The arm 24 is extended r'earwardly beyond the body portion 23 where ithas a downturned end portion 28 in which is mounted an adjusting screw29. The adjusting screw may assume any of various practical forms, suchas that shown in detail in FIG. 7. The screw as here shown has acircumferential groove 31 adjacent its inner end fitted in a slot 32formed in a plate 33 secured to the rear face of the body portion 23.The inner extremity 34 of the screw is fitted in a groove 35 formed inthe rear face of the body portion 23. Upon turning the screw 29, the arm24, with the head A mounted thereon, is moved forwardly or rearwardlyaccording to the direction of the turning of the screw, relative to thebody portion 23, the reaction being provided by the plate 33. The screws26 are, of course, loosened preparatory to making the adjustment of thehead A, after which they are tightened to lock the arm in adjustedposition.

The head A is thus adjustably mounted on the carriage 22 with the tracermember 21 above the drive roll 14. By adjusting the head as justdescribed, the tracer member is positioned for optimum transducingrelationship with the record medium on the carrier C. It will be notedthat such adjustment of the head A is in a direction longitudinally ofthe arm 24 which in turn is on a line transversely of the axis of thedrive roll 14. Upon movement of the transducer head A in eitherdirection from its position of optimum transducing relationship with therecord medium, it, is moved, angularly speaking, a large amount from thevertical, radial plane of the drive roll 14. The optimum positionreferred to, without entering into the details of recording relationrelative to the belt, is to be maintained in the manufacture of thedevice. It will be understood that in production methods of manufacturecertain parts are permitted a relatively wide latitude in tolerance.This tolerance that may otherwise be permitted could result inrelatively great misalignment of the tracer member 21 relative to thebelt or record medium. However, the adjustment enabled by the screw 29enables accurate alignment of the tracer mem her 21 relative to the beltor record medium, without the necessity for having the parts of accuratedimensions.

The carriage 22, shown in detail in the Lorenz application Serial No.489,201 referred to above, is mounted for movement transversely of thebelt and consequent movement of the transducer head A in that direction.The guide rod B which extends transversely of the machine is suitablymounted in frame elements 37 and 38 of the machine. The specific meansfor mounting the carriage on the guide rod includes a hub 39 receivingthe guide rod and slidable thereon. Associated with the carriage 22 ismeans for feeding the carriage and thereby the transducer head A alongthe guide rod B. The carriage includes a depending arm 41 havingtransverse tabs 42 (FIGS. 4 and 6) receiving the hub 3% and enablingrelative pivotal movement thereon. The lower end of the arm 41 has aplate 43 secured thereto which with the lower extremity of the arm 41cooperates with the feed screw F. This feed screw, as shown in FIGS. 5and 6, is journalled in suitable hearings in frame elements, such as theelement 44 at one end and the element 45 (FIG. 9) at the other end. Theplate 43 and the lower extremity of the arm 41 are on efifectivelyopposite sides of the feed screw F whereby the arm 41 is normallymaintained or restrained by the feed screw against pivotal movementrelative to the axis of the guide rod. The surfaces on the plate 43 andarm 41 that engage the feed screw do not eifect threadmg therewith formovement of the carriage, the surfaces being broad and engaging theouter extremities of the threads on the screw. The feed screw F isdriven by suitable means (not shown) within the interior of the machine,but which may be the same motor that drives the drive roll 14.

A compression spring 46 reacting between a collar 47 on the screw andthe adjacent frame element biases the feed screw to a position fromwhich adjustment is made for carrying out certain of the purposes of thepresent invention. This position is to the left in FIG. 6 and to theright in FIG. 5. The feed screw is biased toward the direction of thebeginning margin of the record medium or belt, relative to thetransverse movement of the transducer head A therealong in a transducingoperation. As viewed from the front, as in FIG. 1, the beginning marginof the belt is to the right and the head A moves to the left in thetransducing operation. Adjacent the end 48 of the feed screw oppositethe compression spring as is another collar 49 which serves as stopmeans for limiting the movement of the carriage in that direction, to anelfect to be described hereinbelow.

The carriage 22 in addition to the elements mentioned above includesalso a depending arm 51 which may be an integral extension of the bodyportion 23. The lower end of this arm has mounted thereon a leaf spring52 with a detent or latch 53 engageable with the lower end of the arm41. This detent releasably engages either side of the arm 41 forretaining the head A in a corresponding position. The transducer head ismovable from the transducing position shown in FIG. 4 to anontransducing position raised therefrom, as by rotating the transducerhead clockwise (FIG. 4) about the guide rod B. In the lower ortransducing position of the unit the detent 53 engages the rear side ofthe arm 41 (F16. 4) and in the non-transducing position it engages thefront side, in both cases releasably engaging the arm for normallyretaining the transducer head A in the set position but enabling it tobe moved to the opposite position when the necessary external force isapplied thereto.

A third arm 54 is included in the carriage and is mounted on the hub 39by means of lateral tabs 50 having aligned apertures receiving the hub.This arm is on the same side of the feed screw F as is the arm 51 and onthe outside or front side of the latter. A tension spring 55interconnects the lower ends of the arms 54 and 41. Secured on the arm54 is a plate-like element 56 having an edge 57 (FIG. engageable withthe threads on the feed screw F for feeding the carriage and transducerhead A along the guide rod B. When the head is in its transducingposition the edge 57 engages the threads of the screw, and when the headis raised to non-transducing position, the edge is out of engagementwith the threads, enabling free sliding movement of the carriage andhead along the guide rod as when so manually manipulated.

As in the co-pending Lorenz application, Serial No. 468,907 referred toabove, provision is made for tuning the dictating machine, but thetuning means in the present instance includes improvements over thatdisclosed in the said Lorenz application. The tracer member 21 traces apath on the belt that may be in the neighborhood of .014 inch wide. Thispath is of helical form, as mentioned above, brought about by themovement of the belt surface in linear direction around the rolls, andsimultaneous feeding of the transducer head A in transverse directionalong a path parallel with the axis of the drive roll 14. The linearspeedof the belt and rate of rotation of the feed screw F may beselected for coordination to produce any desired spacing of theconvolutions of the helical path, but it is desired that this spacing beon the order of inch.

After a recording or dictating operation the record medium is placed ina signal reproducing machine. This may be the same machine in which therecording or dictating operation was performed, or it may be anothermachine. The present machine may be utilized either for recording, orfor transcribing or reproducing, but it is possible that a differentmachine, although similar to the present, be utilized for transcribingor reproducing. Vfheu a different machine is used for transcribing orreproducing, and normally when the same dictating machine is used fortranscribing or reproducing, the record medium is removed aftercompletion of the dictating operation and later replaced on a machinefor the reproducing operation. When the record medium is so placed inthe reproducing machine it is, of course, desired that the tracer memberbe accurately aligned with the signal path and not be misalignedrelative there to in a transverse direction along the axis of the roll.This may be made necessary, for example, because of the turning of thebelt end-for-end, i.e., turning it 180 degrees rotation or revolutionabout a transverse axis. In such case the signal path convolutions wouldbe dis placed a distance equal to one-half spacing between theconvolutions, relative to the position of the head A at the completionof the dictating operation. In order to accurately align the tracermember of the transducer with the signal path, in such case, provisionis made for relative shifting movement between the record medium or beltD and the tracer member 21 in direction parallel with the axis of theroll 14. In the preferred arrangement this is accomplished by soshifting the tracer member 21, which is done by moving the transducerhead A along the guide rod B. This is most effectively accomplished byshifting the feed screw F.

This shifting movement is effected by tuning cam means indicatedgenerally at 58 (FIGS. 3, 6, 8, and 9). The parts making up theassembled cam means are best shown in the exploded view of FIG. 8 andinclude a disc-like element 59 which is preferably a stamping andincludes a main portion 61 lying substantially in a plane and having anaperture 62 for mounting it and a tapped hole 63 ad jacent the peripherythereof. This disc-like member includes a cam element 64 at itsperiphery disposed at an angle to the plane of the main portion 61. Thiscam element is formed as by slotting the disc-like member and turning ortwisting the cam portion. The cam means also includes a finger lever 65including a plate portion 66 which engages the disc-like element 59 andhas an aperture 67 for mounting it. The portion 66 has an arcuate slot68 concentric with the axis of the aperture 67. This element alsoincludes an arm 69 having a finger grip portion 7-1 on the outerswinging end thereof. The members 59 and 65 are fitted and securedtogether and to a frame element 72 of the machine by means of a screw 73inserted through the apertures 67 and 62 and through the frame elementwhere it is secured by suitable means such as a nut 74 over which theinner end of the screw 73 is peened. A spring washer 75 is included inthe assembly for tensioning the parts to snug engagement, and a suitablespacer 75:: may be interposed for spacing the assembly relative to theframe element 72. A lock screw 76 is inserted through the slot 68 in theplate portion 66 and threaded into the hole 63 in the disc-like member59. This screw is utilized for locking the members 65 and 59 in relativeangular positions about the axis of the screw 73 in a manner describedbelow.

The cam means 58, in assembly as described above, is mounted on theframe of the machine adjacent the end 43 of the feed screw F (FIG. 6).The feed screw has sliding engagement in its bearing supports and itsend 48 is exposed through the frame element 72. The cam means is mountedin a position radially offset from the feed screw, such as below thefeed screw in position for the cam element 64 to engage the end of thescrew. Upon rotation of the cam means about the axis of the mountingscrew 7-3 the cam element 64, being inclined at an acute angle to thataxis and engaging the end of the feed screw, produces an axial shiftingelfect on the screw.

The arm 69 and finger piece 71 project through a slot 77 in a portion 78of the machine casing, which then is exposed to the front of the machinefor easy access by the operator. The slot 77 defines the range ofswinging movement of the arm, by engagement of the arm with the ends ofthe slot. Upon movement of the finger piece 71 and arm in downwarddirection the cam element 64 effects axial shifting movement of the feedscrew F in inward direction (to the right, FIG. 6), and upon movement ofthe finger piece in upward direction the camming effect is removed andthe compression spring 46 shifts the feed screw in the opposite oroutward direction. The extent of shifting of the feed screw ispreferably an extent at least as great as the transverse spac ng betweenadjacent convolutions of the signal path on the belt. In the casementioned above the spacing is approximately inch. Obviously, anydesired spacing may be utilized but regardless of the magnitude of thespacing, provision is preferably made for shifting the feed screw, andconsequently the transducer head A, an extent at least as great asmentioned so that upon shifting the head in one direction or another itmay be made to register accurately with the signal path.

It is desired that in addition to the tuning operation described, as byshifting the feed screw F, adjustment be made in the cam means 58 forproperly positioning the range of shifting movement of the transducerhead relative to the range of movement of the arm 69. In manufacturingmethods, as was explained above, considerable latitude and tolerance ispermissible from the standpoint of most considerations. However, it isdesired to provide for alignment of the tracer member 21 transversely ofthe belt with particular regard to the starting position thereof oralong the beginning margin of the belt, which in this case is therighthand margin as viewed in FIG. 1. Stop means is provided forlimiting the movement of the tracer member to such beginning position.This stop means preferably consists of the collar 49 on the feed screw(FIGS. and 6) against which the carriage abuts. The desired relation isthat when the unit is moved to the beginning position in which thecarriage abuts the collar 49, the tracer member 21 is in the desiredalignment relative to the beginning margin of the belt. Due to ordinarymanufacturing tolerances, such alignment may not be accurately achievedin mass production assembly of machines. The adjustment between themembers 65 and 59 enables accurate alignment of the character mentionedwithout the necessity of precision in fabricating the parts orassembling them. The cam element 64 has an angular dimensionsubstantially greater than that required for the necessary shifting ofthe feed screw. In the present case this angular dimension is on theorder of twice that actually required for the purpose mentioned. For anygiven setting of the disc-lire element 59, the feed screw F andtransducer assume a definite position. The arm 69 is limited in itsmovements by the ends of the slot 77 and because of the tolerancesmentioned above, the range of movement of the arm 69, as determined bythe slot, may not be positioned, in angular relation to the cam element64, for properly positioning the transducer head A adjacent thebeginning margin of the belt. In such case the lock screw 76 may beloosened and the elements 65 and 59 relatively shifted angularly aboutthe axis of the mounting screw 7 3 to a new position for positioning thecam element 64 with relation to the range of movement of the arm 69 sothat the tracer member 21 is properly aligned with the beginning marginof the belt at the desired point in the range of movement of the arm 69.Thereafter the lock screw 76 is tightened for locking the members 65 and59 in the new relative angular position.

This adjustment of the cam means eliminates the necessity for adjustingthe transducer head A relative to its carriage in transverse direction.It is desired that the tracer member 21 constantly assume a position ina plane perpendicular to the axis of the drive roll 14 and this relationmay be maintained While adjusting the parts for aligning the tracermember 21 with the beginning margin of the belt, by means of the cammeans 58. Additionally, the tracer member 21 may be adjusted relative tothe carriage in direction transversely of the axis of the drive roll 14without interfering in any way with the adjustments made by the cammeans 58.

It is thought that the invention and its attendant advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made in the form, construction and arrangement ofthe parts without departing from the spirit and scope of the inventionor sacrificing all of its material advantages, the form hereinbeforedescribed and illustrated in the drawing being merely a preferredembodiment thereof.

I claim:

1. A dictating machine comprising a belt of magnetic material, a pair ofrolls disposed on spaced parallel axes for mounting the belt formovement through a linear path about said axes including a curvedportion, a magnetic transducer, a carriage mounting said transducer andmovable for moving said transducer between a transducing position and anon-transducing position relative to said belt, feed means for movingsaid carriage and thereby said transducer uniformly transversely of thedirection of movement of said belt, when the transducer is intransducing position, for tracing a helical path on the belt, saidcarriage including an arm rigidly supporting said transducer andslidable longitudinally in a straight line lying in a planeperpendicular to said axes and, when the transduced is in transducingposition, tangent to a circle concentric with said curved portion ofsaid path, means mounted on said carriage for adjustably moving said armand transducer along said line, and means for shifting the transducer alimited distance transversely of said helical path, relative to anyposition of the transducer due to said uniform transverse movement, adistance at least as great 8 as the distance between adjacentconvolutions of said helical path.

2. In a dictating machine, a belt of magnetic material, means for movingthe surface of the belt in a linear path about a transverse axis, amagnetic transducer having a transducing position relative to said belt,feed means for uniformly moving the transducer transversely of thedirection of movement of the belt when the transducer is in transducingposition to trace a helical path on the belt, means for producingshifting movement of the transducer a limited distance transversely ofsaid helical path other than the uniform transverse movement, when thetransducer is in transducing position, and including a movable actuatingelement indirectly engageable with said transducer and a finger leverfor moving the actuating element, said actuating element being operablethrough a range sufficient for shifting the transducer a distance atleast as great as the spacing between adjacent convolutions of saidhelical path, said finger lever being movable through a range sufficientfor operating said actuating element through its range and beingreleasaoly secured thereto for adjustment relative thereto to anyposition within a range equivalent to the range of movement of theactuating element.

3. The invention set out in claim 2 in which said actuating element ismounted for rotary movement and said finger lever is swingable about acommon axis with the actuating element.

4. The invention set out in claim 2 in which the feed means includes afeed screw parallel with said axes, the actuating element is mounted forrotary movement and has a cam element engaging the feed screw andoperative for axially shifting it in response to rotary movement of theactuating element, and said finger lever is swingable about a commonaxis with the actuating element.

5. The invention set forth in claim 2 in which stop means is provided onsaid feed means for limiting movement of the transducer in one directionfor locating it at a predetermined position relative to a beginningmargin of the belt.

6. In a dictating machine, a belt of magnetic material, means for movingthe surface of the belt in a linear path about a transverse axis, amagnetic transducer having a transducing position relative to said belt,feed means for uniformly moving the transducer transversely of thedirection of movement of the belt when the transducer is in transducingposition to trace a helical path on the belt, means for producingrelative shifting movement between said belt and transducer a limiteddistance in direction transversely of said helical path other than theuniform transverse movement, when the transducer is in transducingposition, and including a movable actuating element indirectlyengageable with the shiftably movable one of said belt and transducerand a finger lever for moving the actuating element, said actuatingelement being operable through a range sufficient for causing saidshifting movement a distance at least as great as the spacing betweenadjacent convolutions of said helical path, said finger lever beingmovable through a range sufiicient for operating said actuating elementthrough its range and being releasably secured thereto for adjustmentrelative thereto to any position within a range equivalent to the rangeof movement of the actuating element.

7. A dictating machine comprising a belt of magnetic material, a pair ofrolls disposed on spaced parallel axes for mounting the belt formovement through a linear path about said axes including a curvedportion, a magnetic transducer, a carriage mounting said transducer andmovable for moving said transducer between a transducing position and anon-transducing position relative to said belt, feed means for movingsaid carriage and thereby said transducer uniformly transversely of thedirection of movement of said belt, when the transducer is intransducing position, for tracing a helical path on the belt, saidcarriage including an arm rigidly supporting said transducer andslidable longitudinally of the arm in a straight line lying in a planeperpendicular to said axes and, when the transducer is in transducingposition, tangent to a circle concentric with said curved portion ofsaid path, and means mounted on said carriage for adjustably moving saidarm and transducer along said line.

8. The invention set out in claim 7 wherein said ad ustable moving meansincludes a screw reacting between said arm and another portion of saidcarriage, and the construction includes means for locking the arm, andthereby the transducer, in adjusted position.

9. The invention set out in claim 2 in which the means for moving thesurface of the belt is operable for so moving it selectively in each ofopposite directions,

and in which means is included for moving the transducer when intransducing position conjointly with the belt in each correspondingopposite direction.

References Cited in the file of this patent UNITED STATES PATENTS2,683,038 Saliba Jan. 6, 1954 2,702,710 Conrad Feb. 22, 1955 2,729,453Camras Jan. 3, 1956 2,802,905 Taris Aug. 13, 1957 2,864,892 Perkins Dec.16, 1958 FOREIGN PATENTS 746,243 Great Britain Mar. 14, 1956

